What
are crabs?
Have you ever eaten a crab? Almost everyone knows what a crab looks
like! It has a hard shell, many legs, a pair of pincers. Next time,
look closely at the crab you are eating.
Crabs belong to a group of animals called crustaceans. Other crustaceans
include shrimps and prawns.
Shapes of crabs
The shapes of crabs tell us how they live.
- Can
you guess from the its legs how this crab lives?
- Can
you guess from its pincers what this crab eats?
- Large
crushing pincers: snails and clams
- Spoon
shaped tips: scraping algae
- Sharp,
toothed pincers: snagging fishes
- Small
delicate pincers: harvesting small bits
- Why
is this crab so colourful?
- What
is growing on this crab? Sometimes, swimming crabs have
seaweed and barnacles growing on them. These crabs are usually
infected by parasitic
barnacles.
Marvellous
moulting
- Is
this a crab dead or alive? No it's not alive. No it's
not dead either! It's just an empty shell! Some fascinating moulting
facts
- Crabs
and other hard-shelled animals moult to get bigger. When they
moult they also regenerate lost limbs.
- The soft-shelled
crab that you eat is a crab that has just moulted.
- When
a crab has just moulted and the skin is still soft, it swallows
water so that the skin hardens to be a little larger. That
is why sometimes when you eat crabs they are watery.
- Crabs
can also only mate when the female has just moulted. So sometimes,
males hold on to a female that is just about to moult so that
he can be the first to mate with her.
- More
about moulting
- How
can you tell the difference between a dead crab and a moult?
- A moult
has transparent eyes and is light.
- A dead
crab is heavy and smells bad!
Crabs
are important to the ecosystem
- Like you,
many animals love to eat crabs!
They are an important part of the food chain in the ecosystem. Can
we think of some animals that might eat a crab? Some charismatic
animals to highlight: otters, shorebirds, other crabs, fishes.
Crab
myths to dispel
- Not
all crabs can be eatenIn
fact, some crabs can be highly poisonous. The poison is not destroyed
even by cooking. Don't eat crabs that you caught yourself from
the wild.
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